The following U.S. Pat. Nos. are representative of the most revelant prior art known to the Applicants at the time of filing the application.
639,035, Dec. 12, 1989, G. Hart; 1,616,531, Feb. 8, 1927, C. R. King; 1,928,314, Sept. 26, 1933, L. E. Koss; 2,479,078, Aug. 16, 1949, L. H. Milligan et al.; 3,067,551, Dec. 11, 1962, J. W. Maginnis; 3,867,795, Feb. 25, 1975, W. C. Howard; 4,292,768, Oct. 6, 1981, R. Panetti.
There is a type of grinding operation in which a side face of a grinding wheel is applied to the work being ground rather than the peripheral face. Such a wheel may be attached to the grinding machine in a variety of ways.
One such wheel is the so-called plate mounted wheel such as that described by Milligan et al in U.S. Pat. No. 2,479,078. This wheel is made up of a back plate, shown as B in the drawing, which is permanently attached to a grinding wheel A with a cement or adhesive. The wheel is attached to the shaft of a grinding machine through the hole in the back plate B by a suitable attaching means. Another wheel of this type is that taught by R. Panetti in U.S. Pat. No. 4,292,768. In this case, referring to the drawing, there is a grinding wheel (6) which is permanently and integrally attached to a metal plate (7 and 8), and a clamping flange (9) for clamping the plate of grinding wheel against a support flange. Upon mounting, the upper portion (7) of the mounting plate and the clamping flange (9) are centered around a collar (12) which protrudes from the support flange. The upper part (7) of the mounting plate is held in position, before clamping, by engagement of edges of two radial notches (14) below the retaining studs (16) of the two spindles (15) of the support flange (1). Two locking spindles (19) which are rigidly secured to the clamping flange (9) angularly immobilize the assembly by engagement in two corresponding holes (17) of the support flange. These types of wheels and their method of mounting require that the wheel include a permanently affixed mounting means i.e. the mounting plate is fabricated as part of the wheel.
A further wheel of this type, i.e. one where the grinding surface is a side face of the wheel rather than its peripheral surface, is the subject of U.S. Pat. No. 639,035 to G. Hart. The wheel, which happens to be a segmental wheel, does not include an integral mounting plate such as that taught by Milligan et al or Panetti, as a permanent part of the wheel. Instead the wheel is held and driven by a chuck which is made up of, again referring to the drawing, a circular base (1) with a centrally located hole (2) which is the means through which the chuck is attached to the shaft of a motor. The base (1) has an annular flange (3) extending around its outer edge and a second flange (4) concentric with the outer flange (3) but located within the latter thus forming a channel (5) between them. The grinding wheel (6) is located in the thusly formed channel (5). Clamping plates (7) are located between the inner wall of the grinding wheel and the outer wall of the inner flange (4). Screws (8) pass through holes in the inner flange (4) making contact with the clamping plates (9) forcing them against the inner surface of the wheel which causes the outer surface of the abrasive wheel to be forced against the inner surface of the outer flange (3). Spacer blocks (10) are inserted in the annular space or channel (5) to prevent any rearward movement by the abrasive wheel segments and to reduce the amount of wheel that would be unuseable if the entire volume of the annular channel (5) had to be filled with grinding wheel in order to take advantage of the support provided by the bottom or back surface of the channel (5).
A second example of a chuck arrangement for holding and driving a grinding wheel is that of Koss U.S. Pat. No. 1,928,314 which is a somewhat more complex chucking arrangement than that of the Hart patent. Thus chuck's relevance to the present invention resides in the fact that the chucking device causes or results in a forced contact between the abrasive wheel (again a segmental wheel), the flange (12) of the metal base plate (10) and the wedge member (25). Frequent changing i.e. replacement of the wheel in such a chuck, or a chuck such as that of Hart, will cause substantial wear on those surfaces of the chuck with which the abrasive wheel makes contact not to mention the not infrequent occurance where the chuck is initially not adjusted tightly enough against the wheel so that very damaging slippage between chuck and wheel occurs when the machine is initially applied to the work.
There are also grinding wheel chucks which utilize clamps which forceably grasp the outer periphery or peripheral surface of a cylinder type wheel which is solid as opposed to segmental. The present invention is concerned with the wear on chucking devices caused by both segmental and nonsegmental abrasive wheels and eliminates or greatly reduces such chuck wear.
The present invention is a composite wheel which is monolithic but made up of sections with differing compositions. Composite wheels per se generally, are not new. U.S. Pat. No. 1,616,531 to C. R. King describes a composite wheel consisting of three distinct layers or sections, a hard central abrasive section (10) sandwiched by two addition abrasive sections (11 and 12) which are softer by virtue of the fact that they are bonded with a softer, weaker bond than the bond used in the central section; this type of wheel is a cutting-off wheel and is used in such a manner that the peripheral edge makes contact with and cuts the material being processed. The Maginnis reference U.S. Pat. No. 3,067,551 is another multizoned or multisectional wheel which also grinds on its peripheral face and not a side face. This purpose of the Maginnis wheel is to accomplish with a single wheel, what normally takes two wheels to do i.e. remove a desired amount of metal at an economically rapid rate while imparting a high quality finish to the work piece. This objective is reached by constructing a wheel with a sandwich configuration as shown, in its simpler form, in FIG. 1 of the drawing where the peripheral grinding surface S presents to the work piece, a section C containing coarse abrasive grain for rapid metal removal flanked by two sections F containing fine abrasive. Both types of sections do contain abrasive and abrasive of the same type such as silicon carbide. The wheel is used by causing it to rotate at high speed, bringing the grinding surface S into contact with the work piece at one end and causing wheel to traverse the work piece in a given direction. In the direction of travel, the work piece first is subjected to one of the fine abrasive containing sections F which results in very little metal removal. However, following that leading F section is the coarse abrasive containing C section which does remove a substantial amount of metal. Lastly, the work piece is subject to the other fine abrasive section F which then polishes or removes the rough marks left by the coarse section C. The direction of the wheel is then reversed repeating the process. The Maginnis wheel does not grind on a side face and the entire thickness of the wheel contains highly abrasive particles. The invention wheel differs in that it is used on a side face and contains relatively nonabrasive material in its nongrinding portion.
Lastly, there is U.S. Pat. No. 3,867,795, the Howard patent. The wheel disclosed is used, to some degree, on a side face thereof; it is actually used partially on a side face and partially on the peripheral face. The wheel is also made up of two sections, a primary grinding section or layer (20) and a secondary abrading section (26). Both sections do contact the work piece and do grind i.e. remove metal. The invention wheel by contrast, is not used in such a manner that both sections of the wheel contact the work piece and the back (less abrasive) section is where the holding and driving means makes exclusive contact. The Howard patent is relevant for its teaching of a layered wheel wherein the back layer may contain a less abrasive material, e.g. garnet, silica, emery, flint and quartz. These materials are useable in the wheel of the present invention.